Switching to RSpec for testing

This is the first installment of the potential switch, it illustrates the format of model testing. If anyone has any input on how I can make these tests even better, while maintaining readability, I would really appreciate the help. I purposely only tested one method so that we can focus more on the style versus what is actually being tested. I'm hoping to decide on a style before this PR is merged.  @ferrous26 @zhangsu
The faker calls should probably in a block so that it is lazily evaluated, otherwise creating more than 1 object using the factory will have the same generated value and violate the unique constraint. The same applies to everywhere else. See http://stackoverflow.com/questions/5356387